1. Field of the Invention
The present invention is related to a winding device, particularly for a roll slitter, for winding a material web onto and unwinding a material web off of a winding roll, the winding device including a support device that can be placed against a circumference of the winding roll.
2. Discussion of Background Information
In one of the final manufacturing steps, a paper web is wound into winding rolls, if necessary, after running through a slitting assembly. Very often, a winding core or a winding tube made of cardboard is utilized as the starting point for the winding roll. In particular, when winding fairly wide winding rolls, the winding tube does not possess adequate stiffness. Accordingly, if held at the roll core, i.e., at the center of the winding roll, the winding roll begins to sag or bend in the middle as the diameter, and, therefore, the weight of the roll increases. With such a winding technique, it is generally necessary to also support the winding roll on the circumference. This may be effective in reducing or avoiding sagging, as was recognized in EP 0 289 776 B1. Although this document dealt primarily with unwinding, the problem of supporting a roll of great weight presents itself in a similar manner.
As noted above, as the diameter of the winding roll increases, its weight also increases. Consequently, the force with which the winding roll rests on the support device and, therefore, the contact pressure, also increases with increasing diameter. However, contact pressure is one of the factors that determines the winding tightness (hardness), i.e., the greater the contact force, the greater the winding tightness. However, this occurrence is not desirable because it is more desirable to achieve an opposite winding tightness development over the diameter of the roll, i.e., the roll should be wound tighter in the region of the roll core than on the periphery.
In order to solve this problem, several different approaches are known to those in the art. For example, DE 42 14 713 A1 shows use of a band that is guided over three triangularly arranged supporting rollers, the base of which is arranged to point upward against the direction of gravity. Between the two upper supporting rolls, a free length of the band is arranged and upon which rests the winding roll. When tension of the band is appropriately adjusted, a section of the band contacts the circumference of the winding roll. Accordingly, the force is distributed over a somewhat larger area so that the contact pressure is reduced.
In a solution of this nature, it is relatively difficult to achieve results that are reproducible over the long run because the band changes over time from the stress of the use. While it is possible to compensate for these changes, it is also costly.
Another solution has been disclosed in EP 0 292 451 B1. In this document, one side of the winding roll is arranged to rest against a rider roll. Arranged next to the rider roll, i.e., on the other side, is an additional pair of rolls that is likewise encircled by a band. As the diameter of the winding roll increases, a center point of the winding roll increasingly travels over the roll pair in the direction of the band. In this manner, a better distribution of force should be possible. However, in the end there is a risk that the winding roll will rest a majority of its weight on one or the other of the two rolls of the roll pair and, thus, the winding tightness will becomes too great.